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United States Patent |
6,029,711
|
Koch
,   et al.
|
February 29, 2000
|
Hose for a hose pump
Abstract
A hose for hose pumps is provided. The hose has, in the unloaded state, an
essentially elliptical cross-sectional profile with a long semiaxes ending
in a point, with an outer width B1 of about 0.8 to 10 mm, a maximum outer
height H1 of about 0.4 to 5 mm, the numerical ratio of the outer width B1
to the maximum outer height H1 being about 2:1, and with a wall thickness
of about 0.3 to 2 mm, wherein the hose essentially consists of one of the
elastic materials rubber, silicone rubber, nylon, polyethylene or
polyamide.
Inventors:
|
Koch; Jochim (Ratzeburg, DE);
Loser; Ralf Ernst (Lubeck, DE)
|
Assignee:
|
Drager Medizintechnik GmbH (DE)
|
Appl. No.:
|
288721 |
Filed:
|
April 9, 1999 |
Foreign Application Priority Data
| Apr 11, 1998[DE] | 298 06 660 U |
Current U.S. Class: |
138/118; 138/172; 138/DIG.11 |
Intern'l Class: |
F16L 011/00 |
Field of Search: |
138/128,156,170,177,178,DIG. 11,140,118
|
References Cited
U.S. Patent Documents
377318 | Jan., 1888 | Marshall | 138/177.
|
385109 | Jun., 1888 | Garver et al. | 138/178.
|
2742388 | Apr., 1956 | Russell | 138/156.
|
3201861 | Aug., 1965 | Fromson et al. | 138/140.
|
3624800 | Nov., 1971 | Swick | 138/177.
|
3939875 | Feb., 1976 | Osborn et al. | 138/178.
|
3961486 | Jun., 1976 | Granholm et al. | 138/DIG.
|
3996968 | Dec., 1976 | Bergman et al. | 138/177.
|
4478661 | Oct., 1984 | Lewis | 138/128.
|
4862922 | Sep., 1989 | Kite, III | 138/128.
|
Primary Examiner: Hook; James
Attorney, Agent or Firm: McGlew and Tuttle, P.C.
Claims
What is claimed is:
1. A hose for hose pumps, the hose comprising in the unloaded state:
an essentially elliptical cross-sectional profile with the long semiaxes
ending in a point, with an outer width B1 of about 0.8 to 10 mm, a maximum
outer height H1 of about 0.4 to 5 mm, the numerical ratio of the outer
width B1 to the maximum outer height H1 being about 2:1, and with a wall
thickness of about 0.3 to 2 mm, wherein the hose is formed of one of the
elastic materials rubber, silicone rubber, nylon, polyethylene or
polyamide.
2. The hose in accordance with claim 1, wherein the silicone rubber has a
Shore hardness between 35 and 80 ShA.
3. The hose in accordance with claim 2, wherein the hose consists of a
seamlessly extruded material.
4. The hose in accordance with claim 1, wherein the hose consists of a
seamlessly extruded material.
5. A hose for hose pumps, the hose comprising in the unloaded state:
an upper and a lower wall joined at flat edges defining an interior with an
essentially elliptical cross-sectional profile with the long semiaxes
ending in a point, with an outer width B1 of about 0.8 to 10 mm, a maximum
outer height H1 of about 0.4 to 5 mm, the numerical ratio of the outer
width B1 to the maximum outer height H1 being about 2:1, and with a wall
thickness of about 0.3 to 2 mm, wherein the hose consists of an elastic
material selected from the group consisting of rubber, silicone rubber,
nylon, polyethylene or polyamide.
6. The hose in accordance with claim 5, wherein the silicone rubber has a
Shore hardness between 35 and 80 ShA.
7. The hose in accordance with claim 6, wherein the hose consists of a
seamlessly extruded material.
8. The hose in accordance with claim 5, wherein the hose consists of a
seamlessly extruded material.
Description
FIELD OF THE INVENTION
The present invention pertains to a hose for a hose pump.
BACKGROUND OF THE INVENTION
Hose pumps are used in medical engineering to meter liquids, e.g., to meter
water in a breathing air humidifier. Such pumps are also sometimes
referred to as peristaltic pumps.
Commercially available hose pumps have d.c. motors with sliding collectors,
which operate at relatively high speeds. The service life of these motors
is limited and corresponds, at the most, to a continuous operation for
less than one year; the costs are rather substantial. Collectorless motors
with external commutator are still expensive. For adjustment to the low
speeds needed by a hose pump, these motors are provided with a gear, which
causes additional friction, associated with wear and loss of power of the
motor.
Stepping motors as a drive for hose pumps have a substantially longer
service life, because they run at a lower speed and are therefore
substantially less expensive than d.c. motors. One drawback of such
stepping motors is that they deliver a relatively low torque in relation
to their size, so that the use of a stepping motor instead of a geared
d.c. motor is not readily possible.
To reduce the friction in a hose pump and to make it possible to use a
stepping motor with a relatively low specific torque as a drive motor, a
relatively thin-walled, elastic pump hose was tensioned over the pump
head, so that the rollers of the pump head close individual segments in
the hose, which bring about delivery of the enclosed liquid during the
rotation of the pump head. The pretension of the hose determines the
maximum delivery head and the maximum pump pressure. The friction, which
is caused by this principle, is generated by the friction of the rollers
of the pump head and by the inner friction in the hose material.
One drawback of the latter principle of a hose pump arises from the fact
that a thin-walled, elastic hose with a usual circular cross section is
worn after only a few hours of operation.
SUMMARY AND OBJECTS OF THE INVENTION
The primary object of the present invention is to propose a hose for a hose
pump that has a prolonged service life in operation and a relatively
thin-walled, elastic material is used.
According to the invention, a hose for hose pumps is provided. The hose
has, in the unloaded state, an essentially elliptical cross-sectional
profile with a long semiaxes ending in a point, with an outer width B1 of
about 0.8 to 10 mm, a maximum outer height H1 of about 0.4 to 5 mm, the
numerical ratio of the outer width B1 to the maximum outer height H1 being
about 2:1, and with a wall thickness of about 0.3 to 2 mm, wherein the
hose essentially consists of one of the elastic materials rubber, silicone
rubber, nylon, polyethylene or polyamide.
The silicone rubber preferably has a Shore hardness between 35 and 80 ShA.
The hose preferably consists of a seamlessly extruded material.
One essential advantage of the hose according to the invention is due to
the fact that a more wear-resistant solution is provided for the use of a
thin hose material for the use of a relatively low-torque hose pump motor,
especially a stepping motor.
The energy and power losses due to the inner friction in the hose material
are obviously greatly reduced due to the solution of the invention.
The service life of a hose according to the present invention is
correspondingly up to 100 times that of a hose with a usual circular cross
section made of the same material.
The various features of novelty which characterize the invention are
pointed out with particularity in the claims annexed to and forming a part
of this disclosure. For a better understanding of the invention, its
operating advantages and specific objects attained by its uses, reference
is made to the accompanying drawings and descriptive matter in which a
preferred embodiment of the invention is illustrated.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
The only FIGURE is a cross sectional view through a hose of one exemplary
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings in particular, in the compressed state, not
shown, the hose comprises, when viewed geometrically, two smooth, parallel
layers, with a height corresponding to twice the wall thickness.
To generate vacuum on the suction side, the hose must be hollow on the
inside in the unloaded state and must not be collapsed. The FIGURE shows
the cross section of the hose in the unloaded state.
The hose cross section is shown enlarged 20 times compared with the actual
hose.
The dimensions of the exemplary embodiment are as follows: The wall
thickness is 0.5 mm, the outer width B1 is 5 mm, and the inner width B2 is
4.2 mm. The maximum outer height H1 is 2.5 mm, and the inner height H2 is
1.5 mm. As can be recognized from the FIGURE, the hose has an essentially
elliptical inner cross-sectional profile with the long semiaxes ending in
a point. Concerning the outer contour, the circumferential line ends
laterally in parallel to the long semiaxes of the elliptical
cross-sectional profile and extends symmetrically at right angles at a
distance of 0.5 B1 to the left and right of the mean perpendicular
(perpendicular to the long semiaxes of the elliptical inner
cross-sectional profile).
Experiments have confirmed that in the case of an outer width B1 of about
0.8 to 10 mm, the maximum outer height H1 must be about 0.4 to 5 mm at a
B1:H1 numerical ratio of about 2:1 and a wall thickness of about 0.3 to 2
mm, the hose formed consisting essentially of one of the elastic materials
rubber, silicone rubber, nylon, polyethylene or polyamide.
Silicone rubber with a Shore hardness between 35 and 80 ShA is especially
advantageous.
The selection of the material is also determined by the liquid to be
delivered, besides the elasticity. Silicone rubber is highly compatible
with sterile water and has good durability for the conditions of use in
hospitals and in routine health care in general. Silicone rubber may be
sterilized even at temperatures higher than 100.degree. C. Besides nylon,
polyethylene or polyamide are other suitable hose materials if they are
elastic and have good stretching properties over prolonged periods of use
in prolonged load and release cycles.
The manufacture of a hose according to the present invention as a seamless
extruded product through a corresponding nozzle in the form of an endless
strand, which may be divided as desired, is particularly preferred.
In the preferred case of application in a hose pump, the hose is
pretensioned over the pump head and the rollers of the pump head, so that
the hose is only just sealed securely.
In the case of a pump head with a plurality of rollers (n), each sealing
site must seal only one n-th of the pressure difference. If the hose is in
contact with three rollers due to corresponding guidance in an example
with six rollers, each sealing site must seal only 1/3 of the entire
pressure difference. The liquid located between two rollers is delivered
further during the rotation of the pump head and a delivery pressure is
built up. The delivery capacity of the hose pump can be calculated from
the speed of rotation of the pump head, multiplied by the amount of liquid
enclosed on a complete circumference between the rollers.
The stability of the hose against collapsing due to vacuum in the hose is
determined by the material (elasticity), by the wall thickness and the
geometry of the hose cross section. In the compressed state, the hose
assumes a rectangular cross-sectional shape with double wall thickness and
resembles, on the whole, the eyelids in terms of the characteristics of
the movement and in positioning.
While a specific embodiment of the invention has been shown and described
in detail to illustrate the application of the principles of the
invention, it will be understood that the invention may be embodied
otherwise without departing from such principles.
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